1. Field of the Invention
The present invention relates to orthodontic appliances and more particularly to an appliance for providing lateral expansion of the upper and/or lower posterior segments.
2. Description of the Prior Art
Frequently there is a lack of room for the front (especially lower) permanent incisors when they first erupt into the mouth at 7-9 years of age. This lack of room is frequently anteriorly across the front of the lower jaw because the permanent incisors are considerably larger than the deciduous teeth that preceeded them. If the lack of space is not corrected prior to the eruption of these permanent teeth, they rotate and are displaced out of position upon their eruption. The collagenous fibers then gradually form and hold them in their rotated and crowded position. If the teeth are eventually straightened, even with creation of additional space by whatever means, they frequently rotate back toward their original crowded and rotated positions. When similar teeth are straightened as they erupt at 7 or 8 years of age or shortly after, they tend to stay straight probably due to the collagenous fibers that are formed around these teeth after they were straightened. Since the erupting teeth were not allowed to become rotated and crowded and allowed to stay that way, the fibers were never formed originally in the rotated or crowded position. Therefore, it would be preferable to provide expansion at an early age, before the eruption of the lower permanent incisors at about from a very early age up to about 8 years of age as a form of preventive type orthodontic treatment. Or it can be done later or at any age when it seems appropriate to get expansion of the arches.
A drawback to expanding both the upper and lower posterior segments at the same time is that usually if one arch is expanded, the opposite arch must be expanded with another appliance which results in a mouth full of double appliance and is twice the appliance cost. A custom-made removable-type appliance known in the art as the "Frankel" has been used for expansion on the sides, but this requires that the user, generally a young child, keep the appliance in the mouth for a sufficient amount of time to provide the required effect. As can be expected, voluntary usage of such a device oftentimes leads to less than satisfactory results.